Various research groups have reported on the close interplay between cell shape and stem cell differentiation. For example, it has been shown that cell shape would affect human mesenchymal stem cells (hMSCs) differentiation, and it has been shown that there is interplay between cell shape and focal adhesion assembly. On these fronts, surface patterning is usually required and micro-contact printing (μCP) remains one of the most popular methods of surface patterning.
Micro-contact printing has gained enormous interests due to its simplicity and wide range of applications in the field of biosensor, cell adhesion, cell differentiation, and biomaterials interaction studies. However, when conventional micro-contact printing is applied to soft and/or tacky substrates, issues like substrate sagging and difficulty in stamp removal leads to non-conformances in the patterns generated. Moreover, it is difficult to apply convention micro-contact printing on non-planar surfaces, and it is almost impossible to apply conventional micro-contact printing on surfaces having complex topographies or wavy surfaces.
While conventional micro-contact printing techniques have been satisfactory in the past, in recent emerging researches involving soft tissue engineering, this technique has proved inadequate. Research has shown that the substrate materials for that stem cells culture have to be mechanically compliant with the soft tissues for soft tissue culture. These materials, such as polydimethylsiloxane (PDMS) and polyacrylamide (PA) gel, having Young's modulus values in the range of 40 kPa or less, can be tacky, which can result in the stamp adhering to the tacky substrates and causing distortion in patterns. These drawbacks become increasingly significant as the substrate used gets softer and tackier.
Moreover, conventional PDMS stamps are relatively stiff to allow ease of handling. Therefore, it is not easy to micro-contact print on surfaces having a complex shape such as cylinder, or spherical scaffolds with curvatures.
In view of the above, there is a need for an improved method to micropattern a substrate. In particular, there is a need for an improved method to micropattern a substrate having a soft and/or sticky surface, as well as objects with surfaces having a complex topography.